I have no issues against formal martial arts systems. A LOT of good stuff ... most good stuff... comes from traditional IMAs! But I do believe that the underlying body method itself that powers those IMAs, and learning to fight with it with whatever works from the great wealth of arts out there -- without binding oneself to the limitations of any one system -- will make you a better-rounded fighter. It seems to me that the men who are the greatest fighters within the martial arts, have backgrounds in multiple martial approaches and do not think in the "I do this art, so I have to use this specific technique or approach, even if something else from "outside" works better." In other words, they are "mixed-martial artists" in the truest sense.
The OP was asking about grappling vs. IMA, saying "in such-and-such art they do this, and in so-and-so art they do that," which I think is very limiting -- you restrict yourself to acting in only in certain ways to control an opponent. I am saying that's not the way to go about it. Instead, learn grappling AND learn an IMA... that has actual IMA core body method... and his question will answer itself. And, yeah, continue to train in and enjoy your IMA of choice.